Spain introduced Christianity n the New World to gain favour with the Pope. Pope is considered to the head of the Catholic Church. Spanish spread Christianity because of the Dudum siquidem, issued in 1493 by Pope Alexander VI. The Papal Bull (Inter caetera) approved unclaimed lands to be found and turn the Natives into Christianity. The Pope ordered Christianity to spread in America because he believed in religious supremacy. Spain agreed to follow the request of the Pope to get recognition.
The economy you described in your question is called a market economy. It has free markets and the production of goods and services are determined by the consumers.
